How to Choose (or Make) the Best Mould for Concrete Pot Casting
- Astrid van Essen
- Apr 21
- 4 min read
Updated: Apr 22
Everything You Need to Know to Get Smooth, Stylish Results — Even on Your First Try
If you're starting out with concrete casting at home, your mould is just as important as your mix. A good mould gives your pot structure, texture, and an easy release. In this guide, we’ll cover what to look for in pre-made silicone moulds, how to assess shape and depth, and how to upcycle everyday packaging into reliable DIY moulds — including a must-know trick for plastic bottles.
1. Choosing the Right Mould Material
Silicone Moulds (Buy Smart, Not Just Cheap)
Silicone moulds are one of the best investments for small-scale concrete casting — but not all are created equal.
Thicker is better: Thin silicone often collapses when filled with concrete, distorting the final shape and causing weak points. Look for food-grade or professional casting moulds with a sturdy wall thickness.
Depth matters: If the mould isn’t deep enough, the final piece can crack during curing or when removed. You should aim for a minimum depth of 3–5 cm for most pots and holders.
Reinforced edges help: Moulds with a reinforced rim or base are more stable and easier to move once filled.
Glossy interior = smooth finish: A shiny interior surface will give your pot a sleek, polished appearance with minimal air bubbles.
Plastic Containers
Repurposed plastic bottles, tubs and jars are great for beginners.
Look for containers with flexible sides — these help with unmoulding.
Avoid textured interiors unless you're going for a rustic look.
Always check that the plastic won’t warp under the pressure of wet concrete.
Cardboard or Tins
Perfect for one-time use or testing shapes.
Line with cling film, wax paper, or freezer bags to prevent the concrete from bonding or leaking.
Be aware: these can absorb water, which may affect curing if left too long.
2. Key Mould Features to Look For
Depth & Thickness
Shallow moulds (less than 2 cm) cure quickly but are more fragile and prone to cracking.
Deeper moulds (5 cm or more) provide more structure and are better suited for planters or larger trays.
Shape & Opening Width
Tapered shapes (wider at the top) make it easier to remove the cured piece.
Straight or narrow-necked moulds often require cutting the mould open to prevent the piece from breaking on removal.
Surface Texture
Smooth interiors = polished concrete look.
Want texture? Use lace, leaves, or add sand to the mix — don't rely on a bumpy mould unless it’s intentional.
3. DIY Mould Ideas from Everyday Items
No moulds yet? No problem. Your recycling bin is a goldmine for casting containers.
Top Household Items That Work Well:
Milk or Juice Cartons – Ideal for medium pots. The waxed interior makes release easy. Just trim down to size.
Yoghurt Pots, Hummus Tubs, Takeaway Containers – Excellent for mini planters, tealight holders, or desk trays.
Pringles Tins – Great for tall, cylindrical shapes. Cut away the side to release after curing.
Glass Candle Jars – Lovely for smooth bowls and wax burners. Use mould release spray or line with a bag.
Paper Cups – Surprisingly Effective for Mini Pots. Just peel away after setting.
Bonus Hack: Use Plastic Bottles as Moulds (Just Trim the Rim!)
Plastic bottles make beautifully uniform cylinder moulds — but the top rim is a hidden trap.
Why You Need to Trim It:
The hard plastic ring around the bottle neck can stop your cured pot from sliding out.
Use scissors or a craft knife to cut off the rim before pouring in your mix (wear gloves and be careful not to cut yourself!)
Once set, snip or peel the bottle away from the concrete.
Ideal for: tall incense holders, vase, test tube-style planters, and modern decor pieces.
What’s your biggest challenge when casting concrete pots at home?
0%A- Removing pots from the mould
0%B- Getting a smooth finish
0%C- Finding the right moulds
0%D- Cracking or air bubbles
4. Prepping Any Mould for Success
No matter what kind of mould you’re using, a bit of prep makes all the difference.
Use a mould release spray (or rub with a light oil) to prevent sticking and surface tearing.
Weigh or tape down lightweight moulds so they don’t shift or float as you pour.
Avoid air pockets by tapping the filled mould on a surface or using a cocktail stick to remove bubbles from corners.
Let it cure fully — don’t rush it. Most concrete requires at least 24–48 hours to set before it can be safely removed.
Final Thoughts
The right mould makes concrete casting fun, rewarding, and repeatable. Invest in quality silicone if you’re selling or gifting your pieces, or explore DIY moulds to experiment with new styles. Always test with a small batch, take notes, and reuse whatever you can.
Beautiful design often starts with clever reuse.
🔗 Related Post: How to Protect and Maintain Silicone Moulds for Concrete Casting
FAQs: Concrete Pot Moulds
1. What’s the best type of concrete pot mould for beginners? Silicone moulds are ideal — they’re flexible, reusable, and easy to release once the concrete sets.
2. Can I use any plastic container as a mould? Yes, as long as it has smooth sides and you use mould release or a liner. Avoid containers with narrow openings.
3. How do I stop my concrete from sticking to the mould? Always use a mould release spray or a light coat of oil before pouring your mix.
4. Why did my pot crack when unmoulding? It likely cured too fast, wasn’t deep enough, or the mould was too rigid. Let it cure for 24–48 hours and choose flexible moulds.
5. Can I reuse DIY moulds, such as cartons or bottles? Usually once or twice. They often warp or tear after use — but they’re great for experimenting with shapes.
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